I did my best with this, no I am not an art major. I'll make it neater and fancier some other day, but it's late, and I'm sick, so enjoy. That black thing is one of my cats sleeping, That kinda gives you an idea of how big this is.
1.  2" pipe about 5 or so feet long (barrel)
2.  2" 90 degree elbow
3.  small piece about 4" long of 2" pipe
4.  2" 90 degree elbow
5.  2" x 1" bushing
6.  1" male pipe thread (MPT) adaptor (2 of them)
7.  WaterMaster electric sprinkler valve, hehe. about $13
8.  (Complicated)  I have a 2" x 1" bushing attached to the other 1" MPT adaptor, and a 4" x 2" adaptor connected to the bushing.  Next is a normal 4" coupling connecting this mess to the pipe.
9.  fill valve.  buy one at a auto parts store, drill a hole, put one in, very simple.  also, put in a pressure gauge,  couple bucks. 
10. 4" pipe about 5 feet long (tank)
11. 4" slip cap
12. barrel support, make this out of whatever you want, but it is necessary.  that's a piece of pipe with zip ties on the barrel and tank. 
note:  all connections are slip other than the 1" MPT that make you able to screw this into the electric valve.
use primer! I'm not gonna explain it, read the can.  You don't want this thing exploding(don't overfill), and yes if you do, it will all end up as pieces the size of an eraser imbedded in your pretty little skin.
some advice is to buy an electric pump, or you will be pumping this up for days to get it around 70 psi.  The electric fill falve is easy, connect the two wires to a little battery, or rig up a switch system.  The valve also has a manual switch that you can do also.
Once again, I am not responsible for what you do with this thing, please do not be a retard and point this at someone or any other stupid act like that.
I've seen enough